<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>顶部菜单</title>
    <style>
        /* 全局统一设置 */
        .clearfix::after{
            content: "";
            display: block;
            clear: both;
            width: 0;
            height: 0;
            font-size: 0;
        }
        .menuContainer{
            height: 64px;
            background-color: #000;
        }
        ul{
            list-style: none;
        }
        .menu li{
            float: left;
            margin: 0px 20px;
        }
        .menu>li::after{
            content: "";
            display: block;
            width: 100%;
            height: 2px;
            background-color: #fff;
            transform: scale(0);
            transition: transform 0.5s;
        }
        .menu li:hover::after{
            transform: scale(1);
        }
        .menu li a{
            display: inline-block;
            color: #fff;
            text-decoration: none;
            font-size: 14px;
            padding: 21px 10px;
        }
        .menu li .subMenu{
            padding-left: 0;
            background-color: #000;
            position: relative;
           
            opacity: 0;
            top: -20px;
            
            transition: opacity .5s, top .5s;
        }
        .menu li:hover .subMenu{
            opacity: 1;
            top: 0px;
        }
        /* 孙子层不一样的地方 */
        .subMenu li{
            float: none;
            clear: both;
            margin: 0;
        }
        .subMenu li a{
            /* color: #f00; */
            padding: 10px 10px;
        }
    </style>
</head>

<body>
    <!-- 
        html\css\js
     -->
    <div class="menuContainer">
        <ul class="menu clearfix">
            <li>
                <a href="#">首页</a>
            </li>
            <li>
                <a href="#">产品中心</a>
            </li>
            <li>
                <a href="#">区块链</a>
            </li>
            <li>
                <a href="#">互联网文化</a>
            </li>
            <li>
                <a href="#">迅雷游戏</a>
            </li>
            <li>
                <a href="#">开放能力</a>
            </li>
            <li>
                <a href="#">关于我们</a>
                <ul class="subMenu">
                        <li><a href="#">公司简介</a></li>
                        <li><a href="#">发展历程</a></li>
                        <li><a href="#">公司荣誉</a></li>
                </ul>
            </li>
            <li>
                <a href="#">Investor Relations</a>
            </li>
        </ul>
    </div>
</body>

</html>